Within the past decade, the advent of world-wide electronic communications systems has enhanced the way in which people can send and receive information. In particular, the capabilities of real-time video and audio systems have greatly improved in recent years. In order to provide services such as video-on-demand, video conferencing, and digital video disc (DVD) motion pictures, an enormous amount of bandwidth is required. In fact, bandwidth is often the main inhibitor in the effectiveness of such systems.
In order to overcome the constraints imposed by existing technology, compression systems have emerged. These systems reduce the amount of video and audio data which must be transmitted by removing redundancy in the picture sequence. At the receiving end, the picture sequence is decompressed and may be displayed in real time.
One example of an emerging video compression standard is the Moving Picture Experts Group (“MPEG”) standard. Within the MPEG standard, video compression is defined both within a picture and between pictures. Video compression within a picture is accomplished by conversion of the digital image from the time domain to the frequency domain by a discrete cosine transform, quantization, variable length coding, and Huffman coding. Video compression between pictures is accomplished via a process referred to as “motion estimation”, in which a motion vector plus difference data is used to describe the translation of a set of picture elements from one picture to another. The ISO MPEG2 standard specifies only the syntax of bitstream and semantics of the decoding process. The particular choice of coding parameters and tradeoffs in performance versus complexity is left to the system developers.
Digital Versatile Disc (DVD) is an emerging technology which due to its nature, requires extensive encryption in order to protect the data, such as a motion picture, against unauthorized copying.
DVD is a specification for the content of video, audio and other compressed data to be used as playback video, audio and, for example, subtitle data by a DVD decoder. The DVD video data is specified in the Moving Picture Experts Group (MPEG) standard (ISO/IEC 13818-2). As well as being represented by this standard, the data is also encrypted using the industry's Content Scrambling System (CSS), which produces an encrypted, encoded data stream for DVD playback. The data stream can be decrypted by hardware licensed to perform CSS decryption. Conventionally, CSS decryption occurs at a PCI card, which also conventionally includes MPEG decompression of the encrypted, encoded data signal. The decoded video signal is then transferred to a display device unencrypted. This means that it may be possible to attach a video storage device to the display interface so that it is able to store a copy of the decoded video data signal.
The present invention is directed in one particular aspect to improving upon this conventional DVD processing of the encrypted, encoded data stream.